Rotor blade and structural system for coupling the rotor blade in a rotor hub

ABSTRACT

The rotor hub can include a rotor blade; a rotor yoke; a grip member having an inboard portion, an upper extension, and a lower extension; and a rotor blade having a root end coupled to the upper extension and the lower extension of the grip member with a first bolt, a second bolt, and a third bolt. The first bolt is located on a spanwise axis of the rotor blade. The second bolt is offset from the spanwise axis by a first chordwise distance and is offset from the first bolt by a first spanwise distance. The third bolt is offset from the spanwise axis by a second chordwise distance and is offset from the first bolt by a second spanwise distance.

BACKGROUND

1. Technical Field

The present application relates to a rotor blade, as well as a structural system for coupling the rotor blade to a rotor hub.

2. Description of Related Art

Conventionally, rotor blades have been coupled to the rotor hub in a variety of ways. One conventional rotor blade attachment system involves attaching the rotor blade with two bolts oriented along a chordwise axis at the root end of the rotor blade. Another conventional rotor blade attachment system involves attaching the rotor blade with two bolts oriented along a spanwise axis at the root end of the rotor blade. Though significant improvements in rotor blade attachments have been made, significant room for improvement remains.

There is a need for an improved rotor blade, as well as an improved structural system for coupling the rotor blade to a rotor hub.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the embodiments of the present application are set forth in the appended claims. However, the embodiments themselves, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view of a rotorcraft having a rotor blade, according to an example embodiment;

FIG. 2 is perspective view of the rotor hub, according to an example embodiment;

FIG. 3 is a top view of the rotor hub, according to an example embodiment;

FIG. 4 is a top view of the rotor hub, according to an example embodiment;

FIG. 5 is a top view of the rotor hub, according to an example embodiment;

FIG. 6 is a cross-sectional view of the rotor hub, taken from section lines 6-6 in FIG. 5, according to an example embodiment;

FIG. 7 is a perspective view of a rotor blade, according to an example embodiment; and

FIG. 8 is a partial perspective view of the rotor blade of FIG. 7, according to an example embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the apparatus and method are described below. In the interest of clarity, all features of an actual implementation may not be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

Referring now to FIG. 1 in the drawings, a rotorcraft 101 is illustrated. Rotorcraft 101 has a rotor system 103 with a plurality of rotor blades 105. The pitch of each rotor blade 105 can be selectively controlled in order to selectively control direction, thrust, and lift of rotorcraft 101. Rotorcraft 101 further includes a fuselage 107, anti-torque system 109, and an empennage 111. Rotorcraft 101 further includes a landing gear system 113, to provide ground support for the aircraft. It should be appreciated that rotorcraft 101 is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. Other aircraft implementations can include hybrid aircraft, tilt rotor aircraft, unmanned aircraft, gyrocopters, and a variety of helicopter configurations, to name a few examples.

Referring to FIGS. 2-6, rotor hub 103 is illustrated in further detail. Rotor hub 103 includes a yoke 109 coupled to a mast 113. Each rotor blade 105 is coupled to the yoke 115 with a grip 119. An inboard portion of each grip 119 is secured within an opening of the yoke 115 with a centrifugal force bearing 135. Grip 119 is a single continuous member having an upper extension 137 and a lower extension 139. Rotor blade 105 is attached to the outboard portion of grip 119 with a unique arrangement of a first bolt 129, a second bolt 131, and a third bolt 133. A pitch horn 123 is interposed between rotor blade 105 and the upper and lower extensions 137, 139 of grip 119. A damper 121 is attached between yoke 115 and a damper attachment portion 141 of with pitch horn 123.

During operation, dynamic forces act upon rotor blade 105 and associated components of rotor system 103. Primary dynamic forces include a combination of centrifugal force loading in a centrifugal force direction 145, a chordwise bending in a bending direction 147, and a beamwise bending in a bending direction 149. Such loading must be reacted by the attachment mechanism used to attach the rotor blade 105 to the grip 119. Further, torsional loading about pitch change axis 143 can be experienced from aerodynamic loading as well as pitch change inputs from pitch horn 123. Conventional two-bolt attachment arrangements have several shortcomings. For example, when the two bolts are arranged approximately spanwise, the torsional loading about pitch change axis 143 can induce bending along an axis formed by the two spanwise located bolts. In the conventional two-bolt arrangement wherein the two bolts are arrange approximately chordwise, the beam bending in direction 149 can induce bending along an axis formed by the two chordwise located bolts. In these conventional two-bolt arrangements, the two bolts must be sized in order to react the bending loads, which can add weight since a larger diameter bolt can increase edge distance requirements, bolt weight, and rotor blade structure at the root end.

In contrast to conventional two-bolt arrangements, the embodiments of the present disclosure include a three-bolt triangular pattern that collectively react the operation loads in such a manner so as to reduce the size of the bolts and corresponding attachment lugs in both the rotor blade 105 and grip 119, thereby reducing the overall weight of rotor system 103 and increasing the useful load of the rotorcraft 101. Further, the aerodynamic drag of the three-bolt pattern is actually less than two-bolt chordwise arrangement. Furthermore, utilizing more than three bolts can add unnecessary weight, and further add complexity to the manual rotor blade folding procedure.

The three rotor blade attachment bolt arrangement includes the first bolt 129, which is the most inboard of the three bolts, and lies upon a center spanwise plane of rotor blade 105. The three rotor blade attachment bolt arrangement also includes the second bolt 131 and the third bolt 133 that are aligned along a chordwise plane, and offset from the first bolt 129 in an outboard spanwise direction by a distance D1. The second bolt 131 and the third bolt 133 are offset from the center spanwise plane by chordwise distances C1 and C2, respectively. In the example embodiment, C1 is equal to C2.

The combination and arrangement of the first bolt 129, the second bolt 131, and the third bolt 133 for attachment of the rotor blade 105 to grip 137 has unique advantages. First regarding the beam bending in direction 149, if first bolt 129 weren't present, then second bolt 131 and third bolt 133 would be subject to relatively large bending forces from the beam bending in direction 149 due to the second bolt 131 and third bolt 133 being aligned in a chordwise direction. However, the presence of first bolt 129 acts to greatly reduce the bending forces on second bolt 131 and third bolt 133 by creating a heel/toe effect. Secondly regarding torsionally forces approximately about pitch change axis 143, if either of second bolt 131 or third bolt 133 weren't present, then an input from pitch horn 123 or aerodynamic force, for example, would act to create relatively large bending forces about an axis formed between the first bolt 129 and either of the second bolt 131 or the third bold 133. However, the presence of both second bolt 131 and third bolt 133, in addition to first bolt 129, acts to greatly reduce the bending forces by creating a heel/toe effect.

Further, by locating first bolt 129 inboard to the chordwise oriented second bolt 131 and third bolt 133, the rotor blade 105 can taper down or become more narrow at the root end. The tapering of rotor blade 105 at the root end allows for clearance between the root end of rotor blade 105 and the damper attachment portion 141 of pitch horn.

Referring now also to FIGS. 7 and 8, rotor blade 105 is described in further detail. Rotor blade 105 can have a leading 701, a trailing edge 703, a root end 705 and a tip end 707. It should be appreciated that rotor blade 105 can take on a wide variety of configurations. For example, rotor blade 105 can have a degree of built-in twist between root end 705 and tip end 707. Describing another example, rotor blade 105 can have an anhedral tip, or any other desirable aerodynamic profile. Rotor blade 105 includes holes 709, 711, and 713 which provide corresponding apertures for bolts 129, 131, and 133, respectively. Thus, the further disclosure herein regarding the location of bolts 129, 131, and 133, also applies to the location of holes 709, 711, and 713 on rotor blade 105. It should be appreciated that holes 709, 711, and 713 can include bushings, or similar, located therein as a bearing surface for the shanks of bolts 129, 131, and 133.

Rotor blade 105 can include a forward taper 715 and an aft taper 717 that each taper toward a centerline axis of the rotor blade until joining at a rounded portion 719. Rounded portion 719 can have a radius that is a function of a desired edge distance from hole 709.

In FIGS. 2-4, first bolt 129 and third bolt 133 are illustrated as quick removable expandable bolts configured to be removed without the need for a tool. A pin can be removed from the lower portion, allowing the handle to be pivoted, which actuates a cam member allowing the bolt to be removed. Once the first bolt 129 and the third bolt 133 are removed, the rotor blade 105 is free to be rotated about second bolt 131. It should be appreciated that some rotorcraft operators don't have a requirement for the folding of the rotor blades 105; as such, all of the first bolt 129, the second bolt 131, and the third bolt 133 can be conventional bolts. Furthermore, FIGS. 5 and 6 illustrate all of the first bolt 129, the second bolt 131, and the third bolt 133 as conventional bolts.

The embodiments herein are illustrated with regard to a main rotor assembly on a rotorcraft; however, it should be appreciated that the embodiments may be adaptable to a tail rotor assembly.

The particular embodiments disclosed above are illustrative only, as the apparatus may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Modifications, additions, or omissions may be made to the apparatuses described herein without departing from the scope of the invention. The components of the apparatus may be integrated or separated. Moreover, the operations of the apparatus may be performed by more, fewer, or other components.

Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below.

To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim. 

1. A rotor hub comprising: a rotor blade; a rotor yoke; a grip member having an inboard portion, an upper extension, and a lower extension; and a rotor blade having a root end coupled to the upper extension and the lower extension of the grip member with a first bolt, a second bolt, and a third bolt; wherein the first bolt is located on a spanwise axis of the rotor blade, the second bolt is offset from the spanwise axis by a first chordwise distance and is offset from the first bolt by a first spanwise distance, the third bolt is offset from the spanwise axis by a second chordwise distance and is offset from the first bolt by a second spanwise distance.
 2. The rotor hub according to claim 1, further comprising: a pitch horn coupled to the rotor blade.
 3. The rotor hub according to claim 1, further comprising: a pitch horn at least partially interposed between the upper extension of the grip member and the rotor blade, as well as between the lower extension of the grip member and the rotor blade.
 4. The rotor hub according to claim 1, further comprising: a pitch horn that is coupled to a pitch link and to a damper, the damper also being coupled to the rotor yoke.
 5. The rotor hub according to claim 1, wherein at least one of the first bolt, the second bolt, and the third bolt is a quick release bolt having handle member that can be actuated.
 6. The rotor hub according to claim 1, wherein the spanwise axis is the centerline of the rotor blade.
 7. The rotor hub according to claim 1, wherein the first spanwise distance is equal to the second spanwise distance.
 8. The rotor hub according to claim 1, wherein the first spanwise distance has a dissimilar magnitude to that of the second spanwise distance.
 9. The rotor hub according to claim 1, wherein the first chordwise distance is of equal magnitude but opposite direction to the second chordwise distance.
 10. The rotor hub according to claim 1, wherein the first chordwise distance is of dissimilar magnitude and opposite direction to the second chordwise distance.
 11. The rotor hub according to claim 1, further comprising: a first hole, a second hole, and a third hole in the rotor blade, the first hole being located to accept the first bolt, the second hole being located to accept the second bolt, and the third hole being located to accept the third bolt.
 12. The rotor hub according to claim 11, further comprising: a bushing located in each of the first hole, the second hole, and the third hole.
 13. The rotor hub according to claim 1, wherein rotor hub is a main rotor hub for a rotorcraft.
 14. A rotor blade comprising: an airfoil member having a root end portion, a tip end portion, a leading edge portion, and a trailing edge portion; wherein the root end portion includes a first hole, a second hole, and a third hole that are configured for attaching the rotor blade to a rotor hub, the first hole being located on a spanwise axis of the airfoil member, the second hole being offset from the spanwise axis by a first chordwise distance and being offset from the first hole by a first spanwise distance, the third hole being offset from the spanwise axis by a second chordwise distance and being offset from the first hole by a second spanwise distance.
 15. The rotor blade according to claim 14, further comprising: a bushing located in each of the first hole, the second hole, and the third hole.
 16. The rotor blade according to claim 14, wherein the first spanwise distance is equal to the second spanwise distance.
 17. The rotor blade according to claim 14, wherein the first spanwise distance has a dissimilar magnitude to that of the second spanwise distance.
 18. The rotor blade according to claim 14, wherein the first chordwise distance is of equal magnitude but opposite direction to the second chordwise distance.
 19. The rotor blade according to claim 14, wherein the first chordwise distance is of dissimilar magnitude and opposite direction to the second chordwise distance.
 20. The rotor blade according to claim 14, wherein the root end includes a first taper and a second taper that form a narrowing of the rotor blade and join at a rounded portion that forms the most inboard part of the airfoil member. 